继承 NSMutableDictionary 并使用 NSKeyedArchiver 序列化的自定义对象无法反序列化

Question

类未正确取消存档。 请参阅下面的代码示例。

@interface A : NSMutableDictionary 
@end
@implementation A
- (void)encodeWithCoder:(NSCoder *)aCoder
{
}
- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder
{
if (self = [super init]) {
}   
return self;
}
@end

@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
A *a = [[A alloc] init];
NSMutableDictionary *dict = [NSMutableDictionary new];
dict[@"some"] = a;
NSData *archive = [NSKeyedArchiver archivedDataWithRootObject:dict];
dict = [NSKeyedUnarchiver unarchiveObjectWithData:archive];
NSLog(@"%@",dict);
}

在unarchiveObjectWithData调用后，字典包含对键@"some"，但对象是NSMutableDictionary而不是A类。当unarchiveObjectWithData调用时，不会发生initWithCoder调用。 那么，如何使它的代码工作呢？为什么继承 NSMutableDictionary 的类没有反序列化？

Answer 1

此方法：

- (void)encodeWithCoder:(NSCoder *)aCoder
{
}

包含对象对自身进行编码的指令，即"不执行任何操作"。 它应该说的是：

- (void)encodeWithCoder:(NSCoder *)aCoder
{
// perform the inherited behavior or encoding myself
[super encodeWithCoder:encoder];
}

再次编辑，这个测试类以最简单的方式子类NSMutableDictionary：通过在其实现中隐藏一个可变字典实例并提供原始方法(PLUSencodeWithCoder)

#import "MyDict.h"
@interface MyDict ()
@property(strong) NSMutableDictionary *internalDictionary;
@end
@implementation MyDict
// changed to the default init for the "new" constructor
- (id)init {
self = [super init];
if (self) {
_internalDictionary = [[NSMutableDictionary alloc] init];
}
return self;
}
- (NSUInteger)count {
return [self.internalDictionary count];
}
- (id)objectForKey:(id)aKey {
return [self.internalDictionary objectForKey:aKey];
}
- (void)setObject:(id)anObject forKey:(id<NSCopying>)aKey {
return [self.internalDictionary setObject:anObject forKey:aKey];
}
- (void)removeObjectForKey:(id)aKey {
return [self.internalDictionary removeObjectForKey:aKey];
}
- (NSEnumerator *)keyEnumerator {
return [self.internalDictionary keyEnumerator];
}
// added encoding of the internal representation
- (void)encodeWithCoder:(NSCoder *)aCoder {
[super encodeWithCoder:aCoder];
[aCoder encodeObject:_internalDictionary forKey:@"internalDictionary"];
}
// added decoding of the internal representation
- (id)initWithCoder:(NSCoder *)aDecoder {
self = [super initWithCoder:aDecoder];
if (self) {
_internalDictionary = [aDecoder decodeObjectForKey:@"internalDictionary"];
}
return self;
}
- (Class)classForCoder {
return self.class;
}
@end

再次编辑，这次完全使用您的测试：

MyDict *a = [MyDict new];
a[@"hi"] = @"there";
NSMutableDictionary *dict = [NSMutableDictionary new];
dict[@"some"] = a;
NSData *archive = [NSKeyedArchiver archivedDataWithRootObject:dict];
dict = [NSKeyedUnarchiver unarchiveObjectWithData:archive];
NSLog(@"%@", dict);

原木。。。

{ 一些 = { 嗨 = 那里; };}